Modern work implements, such as the articulated arms of backhoes, excavators, feller bunchers, cranes, and the like can be moved with several degrees of freedom. For example, a backhoe arm may comprise a boom pivotally mounted to a vehicle at a first joint, a stick pivotally mounted to the end of the boom at a second joint and a bucket pivotally mounted at the end of the stick at a third joint. Actuators are coupled between the various members which make up the arm. The actuators may be used under the control of an operator to adjust the position of each of the pivoting joints. The operator guides the operation of the work implement by manipulating several controls. The controls may be levers, joysticks, foot pedals and the like. The operator's inputs to the controls affect the direction and speed of motion of the work implement.
The control systems for work implements are generally not completely intuitive. An operator must have much practice before he or she can reliably use the control system to control the work implement accurately. Further, even an experienced operator can readily become fatigued because current control systems require significant concentration by the operator. A fatigued operator is more likely to make mistakes than a well-rested operator. When the work implement is a large powerful machine, such as an excavator or a large backhoe, mistakes can cause great damage to the work implement itself or to surrounding machines or structures.
Various prior patents describe control methods or control systems for work implements which attempt to provide an intuitive interface to an operator. For example, Canadian patent No. 1,330,584 describes a control system which determines how to move the articulated arm of a robot so that an endpoint of the arm is moved to a target point. The method involves generating a pseudo-inverse Jacobian matrix. The method has the problem that the arm does not follow a desired trajectory as accurately as would be desired. Further, devices according to the invention tend to be very finicky to maintain.
Allen et al. U.S. Pat. No. 5,160,239 discloses another control system for a backhoe or the like.
Industrial robots are used for various tasks in industry. Such robots are programmed in advance to guide work implements along predetermined paths. Various methods have been developed to allow such robots to follow the desired predetermined paths under changing conditions accurately. These methods are not generally applicable for use in machines operated by human operators because, in general, the work implements of such machines must follow paths which are not predetermined.
There is a continuing need for a control system for work implements which provides a human operator with intuitive control over the work implement and allows the operator to accurately guide the work implement along a desired trajectory with minimum effort.